Programmatic navigation in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What happens when this SwiftUI button is tapped?

Consider this SwiftUI code snippet. What is the visible result when the button is tapped?

iOS Swift

struct ContentView: View {
  @State private var isDetailActive = false
  var body: some View {
    NavigationView {
      VStack {
        NavigationLink(destination: Text("Detail View"), isActive: $isDetailActive) {
          EmptyView()
        }
        Button("Go to Detail") {
          isDetailActive = true
        }
      }
    }
  }
}

A The app navigates to a new screen showing "Detail View" text.

B Nothing happens because NavigationLink is hidden.

C The button causes a crash due to missing NavigationLink label.

D The button toggles a boolean but does not navigate.

💡 Hint

Think about how NavigationLink with isActive binding works in SwiftUI.

The NavigationLink is activated programmatically by setting isDetailActive to true, causing navigation to the destination view.

❓ lifecycle

intermediate

What is the effect of calling pushViewController in UIKit?

In UIKit, what happens when you call navigationController?.pushViewController(newVC, animated: true)?

A The newVC is presented modally over the current view.

B The current view controller is replaced without animation.

C The newVC is added on top of the navigation stack and shown with animation.

D The app crashes because pushViewController requires a storyboard.

💡 Hint

Think about how navigation stacks work in UIKit.

pushViewController adds the new view controller to the navigation stack and shows it with animation if requested.

📝 Syntax

advanced

Which Swift code correctly performs programmatic navigation in SwiftUI?

Select the code snippet that correctly navigates to DetailView when a button is pressed.

iOS Swift

struct ContentView: View {
  @State private var showDetail = false
  var body: some View {
    NavigationView {
      VStack {
        Button("Show Detail") {
          showDetail = true
        }
        // NavigationLink here
      }
    }
  }
}

A NavigationLink(destination: DetailView(), isActive: showDetail) { Text("Go") }

B NavigationLink(destination: DetailView(), isActive: $showDetail) { EmptyView() }

C NavigationLink(isActive: showDetail, destination: DetailView()) { EmptyView() }

D NavigationLink(destination: DetailView()) { Button("Show Detail") { showDetail = true } }

💡 Hint

Check the correct use of isActive binding in NavigationLink.

Option B correctly binds isActive to $showDetail and uses an EmptyView as label for programmatic navigation.

🔧 Debug

advanced

Why does this UIKit navigation code fail to show the new screen?

Given this code snippet, why does tapping the button not navigate to NewViewController? class ViewController: UIViewController { @IBAction func buttonTapped(_ sender: UIButton) { let newVC = NewViewController() newVC.modalPresentationStyle = .fullScreen } }

A Because modalPresentationStyle must be set after presenting.

B Because buttonTapped is missing @objc attribute.

C Because NewViewController must be loaded from storyboard.

D Because newVC is created but never pushed or presented.

💡 Hint

Check if the new view controller is actually shown.

The code creates newVC but does not call pushViewController or present, so no navigation occurs.

🧠 Conceptual

expert

What is the main difference between programmatic navigation and declarative navigation in iOS?

Choose the best explanation of the difference between programmatic navigation (UIKit) and declarative navigation (SwiftUI).

A Programmatic navigation uses explicit commands to push or present views, while declarative navigation uses state bindings to describe navigation paths.

B Programmatic navigation requires storyboards, declarative navigation does not.

C Declarative navigation is only for modal views, programmatic is for push navigation.

D Programmatic navigation is faster at runtime than declarative navigation.

💡 Hint

Think about how navigation is triggered in UIKit vs SwiftUI.

UIKit navigation is done by calling methods to push or present views. SwiftUI navigation is controlled by state variables that describe navigation state declaratively.